Results of a bench mark test on the crack opening and leak rate calculation

1995 ◽  
Vol 61 (1) ◽  
pp. 35-39 ◽  
Author(s):  
H. Grebner
Keyword(s):  
Crack Opening ◽  
Leak Rate ◽  
Bench Mark ◽  
Mark Test ◽  
Rate Calculation

Leak Rates Through Complex Crack Paths: Update on the Latest Developments From the European Project ATLAS+

2019 ◽  
Author(s):  
Peter Gill ◽  
Tomas Nicak ◽  
Brian Daniels ◽  
Florian Obermeier
Keyword(s):  
Crack Opening ◽  
Crack Size ◽  
Weld Interface ◽  
Leak Rate ◽  
Test Case ◽  
Two Phase ◽  
European Project ◽  
Fea Model ◽  
Rate Calculation ◽  
Leak Before Break

Abstract Leak-before-Break assessments require a reliable method to obtain leakage rates from narrow cracks. The ability to predict leakage accurately is crucial to the overall success of Leak-before-Break arguments as the detection capability and limiting crack size are often very small. This can make it difficult to achieve the desired margin between limiting defect size and the crack size required for detectable leakage. The resulting narrow flow paths (< 0.1mm) relative to the wall thickness (> 10mm) necessitates the use of complex thermodynamic and friction models in the leak rate calculation. A method to calculate leakage rates through complex paths was presented in PVP2015-45468 using an ordinary differential equation (ODE) for Mach number. This model was developed to account for crack opening displacements that vary non-linearly through the wall of a pipe. This situation typically arises when there is a through wall crack at a weld, where significant residual stresses are present. This paper considers an FEA model of a plate with a weld residual stress (WRS) profile applied. The WRS is prescribed with nodal displacements, and the COD is calculated from post processing of the elastic stress analysis solution. This results in a COD function in terms of the distance through the wall, which can then be used in the leak rate calculation. Comparisons are made with the R6 methodology recommended software DAFTCAT and the benefits of using the ODE method are discussed. In collaboration with Framatome, Germany, a test case based on the previous European project STYLE was considered. The test case involves a Type 316L Stainless Steel pipe with a girth weld, and the FEA model includes postulated through wall defects at the weld interface to assess crack opening displacements. This model will be used to extract crack opening displacements and calculate leak rates using various methods. Two phase flow will be considered for this test case as the pipe geometry is very relevant to PWRs.

Crack-Opening Displacement and Leak-Rate Calculations for Full Structural Weld Overlays

2009 ◽  
Author(s):  
D.-J. Shim ◽  
E. Kurth ◽  
F. Brust ◽  
G. Wilkowski ◽  
A. Csontos ◽  
...  
Keyword(s):  
Crack Opening ◽  
Nuclear Industry ◽  
Leak Rate ◽  
Opening Displacement ◽  
Primary Coolant ◽  
Pressurized Water ◽  
Weld Overlay ◽  
Water Reactors ◽  
The Impact ◽  
Weld Overlays

Full structural weld overlays have been used in the U.S. nuclear power industry for over twenty years in boiling water reactors (BWRs). Primary water stress corrosion cracking (PWSCC) in nickel-based dissimilar metal welds (DMWs) has been experienced in pressurized water reactors (PWRs) since the early 1990s. As a result, the nuclear industry is implementing full structural weld overlays (FSWOL) as a PWSCC mitigation technique that may be used on primary coolant lines previously approved for Leak-Before-Break (LBB). This work investigates the effect of the FSWOL on the leakage behavior of these lines with postulated defects. In this paper, finite element (FE) based crack-opening displacements (CODs) were developed for pipes with a FSWOL with postulated complex cracks. The COD solutions were then employed in standard leak-rate calculations, where equivalent crack morphology parameters were developed to consider a flow through two different crack morphologies, i.e., PWSCC through the DMW and corrosion fatigue through the weld overlay. The results of the sensitivity study and a discussion on the impact of the weld overlay on the leakage behavior concludes this paper.

Experimental and Analytical Leak Characterization for Axial Through-Wall Cracks in a Liquids Pipeline

2014 ◽  
Author(s):  
Mohamed R. Chebaro ◽  
Nader Yoosef-Ghodsi ◽  
David M. Norfleet ◽  
Jason H. Bergman ◽  
Aaron C. Sutton
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Internal Pressure ◽  
Crack Opening ◽  
Full Scale ◽  
Leak Rate ◽  
Propagation Mechanism ◽  
Element Analysis ◽  
Fea Model ◽  
Experimental Findings

Three pipeline sections containing defects of interest were non-destructively tested in the field, cut out and shipped to a structural laboratory to undergo full-scale testing. The common objectives of the experiments were to determine (1) the leak initiation pressure and (2) the leak rate at various specified internal pressures. While two spools (Specimens A and B) contained through-wall cracks, the third (Specimen C) had a partial through-wall crack with similar characteristics. The capacity of through-wall defects to withstand a level of internal pressure without leaking is due to the resultant local, compressive hoop residual stresses. Specimen C underwent full-scale pressure cycling to further comprehend the crack propagation mechanism in order to correlate it to field operation and analytical fatigue life predictions. To enhance the understanding of the physical crack behaviour as a function of internal pressure, a comprehensive finite element analysis (FEA) model was built using SIMULIA’s Abaqus software. The model inputs incorporated results from the above-mentioned laboratory tests, in addition to extensive radial, circumferential and axial residual stress measurements using the X-ray diffraction (XRD) technique, obtained on three pipe spools cut out from the same line. The resulting crack opening parameters from FEA were input into a closed-form fluid mechanics (FM) model, which was calibrated against a computational fluid dynamics (CFD) model, to determine the corresponding leak initiation pressures and leak rates. These outcomes were then compared to experimental findings. The FEA and FM models were subsequently employed to carry out a parametric study for plausible combinations of feature geometries, material properties, operational pressures and residual stresses to replicate field conditions. The key outcome from this study is the experimental and analytical demonstration that, for given fluid properties and pressures, the leak threshold and leak rate for through-wall cracks are primarily dependent upon the crack geometry and local residual stress distributions.

Development of a Crack Opening Displacement Assessment Procedure Considering Change of Compliance at a Crack Part in Thin Wall Pipes Made of Modified 9Cr-1Mo Steel

2018 ◽  
Author(s):  
Takashi Wakai ◽  
Hideo Machida ◽  
Manabu Arakawa ◽  
Seiji Yanagihara ◽  
Ryosuke Suzuki ◽  
...  
Keyword(s):  
Crack Opening Displacement ◽  
Work Hardening ◽  
Crack Opening ◽  
Large Diameter ◽  
Assessment Method ◽  
Leak Rate ◽  
Thin Wall ◽  
Opening Displacement ◽  
Thin Walled ◽  
Small Work

This study was carried out to establish crack opening displacement (COD) evaluation methods used in Leak-Before-Break (LBB) assessment of thin-walled large-diameter pipes of the Sodium cooled Fast Reactors (SFRs). For the pipes of SFR, the continuous leak monitoring will be adopted as an alternative to a volumetric test of the weld joints under conditions that satisfy LBB. The sodium pipes are made of ASME Gr.91 (modified 9Cr-1Mo steel). Thickness of the pipes is small, because the internal pressure is very small. Modified 9Cr-1Mo steel has a relatively large yield stress and small work hardening coefficient comparing to the austenitic stainless steels which are currently used in the conventional plants. In order to assess the LBB behavior of the sodium pipes made of modified 9Cr-1Mo steel, the coolant leak rate from a through wall crack must be estimated properly. Since the leak rate is strongly related to the crack opening displacement (COD), an appropriate COD assessment method must be established to perform LBB assessment. However, COD assessment method applicable for SFR pipes — having thin wall thickness and made of small work hardening material — has not been proposed yet. Thus, a COD assessment method applicable to thin walled large diameter pipe made of modified 9Cr-1Mo steel was proposed in this study. In this method, COD was calculated by classifying the components of COD; elastic, local plastic and fully plastic. In addition, the verification of this method was performed by comparing with the results of a series of four-point bending tests using modified 9Cr-1Mo steel pipe having a circumferential through wall notch. As a result, in some cases, COD were overestimated especially for large cracks. Although the elastic component of COD, δEE, is still over-estimated for large cracks, leak evaluation from small cracks is much more important in LBB assessment. Therefore, this study recommends that only the elastic component of COD, δEE, should be adopted in LBB assessment of SFR pipes.

Coupling currents losses bench mark test of ITER subsize conductor

1996 ◽  
Vol 32 (4) ◽  
pp. 2826-2829 ◽  
Author(s):  
P. Bruzzone ◽  
Chen-yu Gung ◽  
C. Meuris ◽  
H.H.J. ten Kate
Keyword(s):  
Bench Mark ◽  
Mark Test

Leak rate calculation for LBB analysis in high temperature gas-cooled reactors

2010 ◽  
Vol 240 (10) ◽  
pp. 3231-3237 ◽  
Author(s):  
Xiaowei Li ◽  
Li Shi ◽  
Zhengming Zhang ◽  
Xiaotian Li
Keyword(s):  
High Temperature ◽  
Leak Rate ◽  
Rate Calculation ◽  
High Temperature Gas

scholarly journals EVALUATION OF THE PERFORMANCE OF THE HYBRID LATTICE BOLTZMANN BASED NUMERICAL FLUX

2016 ◽  
Vol 42 ◽  
pp. 1660152
Author(s):  
H. W. ZHENG ◽  
C. SHU
Keyword(s):  
Lattice Boltzmann ◽  
Numerical Scheme ◽  
Navier Stokes ◽  
Bench Mark ◽  
Test Cases ◽  
Numerical Flux ◽  
Mark Test ◽  
Key Factor ◽  
The Stability ◽  
Stability And Accuracy

It is well known that the numerical scheme is a key factor to the stability and accuracy of a Navier-Stokes solver. Recently, a new hybrid lattice Boltzmann numerical flux (HLBFS) is developed by Shu's group. It combines two different LBFS schemes by a switch function. It solves the Boltzmann equation instead of the Euler equation. In this article, the main object is to evaluate the ability of this HLBFS scheme by our in-house cell centered hybrid mesh based Navier-Stokes code. Its performance is examined by several widely-used bench-mark test cases. The comparisons on results between calculation and experiment are conducted. They show that the scheme can capture the shock wave as well as the resolving of boundary layer.

scholarly journals A Trial of Bench Mark Test for PIV

1997 ◽  
Vol 17 (Supplement1) ◽  
pp. 163-166 ◽  
Author(s):  
Hiroshi HAYAMI ◽  
Koji OKAMOTO ◽  
Shin-ichiro ARAMAKI
Keyword(s):  
Bench Mark ◽  
Mark Test
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